A first solution consists in equipping the first aircraft, called the lead aircraft, with a radio transmitter broadcasting a directional beam and in equipping the wing aircraft with receivers able to receive the transmission from the lead aircraft. The wing aircraft lock(s) themselves (itself) at the maximum transmitted by the lead aircraft. This solution is implemented above all in military aircraft formations. The transmitter and receiver system is well known by the name TACAN, for “TACtical Air Navigation”. This solution has the drawback of only providing the wing aircraft with the direction of the lead aircraft.
Another solution consists in equipping the lead aircraft with a transmitter freely broadcasting its position and in equipping the wing aircraft with receivers able to receive the transmission from the lead aircraft. The wing aircraft analyzes the sequence of positions of the lead aircraft in real time and deduces from this the trajectory to be followed and the speed in order to maintain the specified interval. A transmitter system freely transmitting the position of an aircraft is well known by the name ADSB, for “Automatic Dependent Surveillance Broadcast”.
These two solutions are purely corrective and lead to instabilities in the interval separating two aircraft. The result is what is referred to as traffic “accordion”. Consequently the specified interval may not fall below a certain value without leading to collision risks between aircraft.